The evidence, card by card
Every study we lean on, laid out the same way — design, who was studied, what it
found, and where it falls short — each with a real, clickable source. For how we
weigh them, see how we research.
Mechanism
Carbohydrate restriction elicits metabolic effects similar to fasting
Biyikoglu et al. · European Journal of Nutrition · 2025
- Design
- Randomized crossover (acute, controlled feeding)
- Who
- Healthy adults
- Found
- Acutely restricting carbohydrate produced post-meal metabolic effects (lower glucose and insulin, a tilt toward fat oxidation) similar to fasting — the core premise behind carb fasting.
- Caveat
- Acute, mechanistic study of post-meal metabolism — not a long-term weight-loss or outcomes trial.
DOI 10.1007/s00394-025-03646-5 · PMID 40111529
Low-carb
Keto-Med: ketogenic vs Mediterranean-plus diet (randomized crossover)
Gardner et al. · American Journal of Clinical Nutrition · 2022
- Design
- Randomized crossover, two 12-week diet phases
- Who
- Adults with prediabetes or type 2 diabetes
- Found
- HbA1c was not different between the diets; triglycerides fell more on keto; LDL-cholesterol rose on keto and fell on the Mediterranean phase; fiber and some nutrients were lower on keto.
- Caveat
- Short diet phases; the LDL response varied between individuals.
DOI 10.1093/ajcn/nqac154 · PMID 35641199
Low-carbohydrate diets for type 2 diabetes remission
Goldenberg et al. · BMJ · 2021
- Design
- Systematic review & meta-analysis of RCTs
- Who
- Adults with type 2 diabetes
- Found
- Low-carbohydrate diets improved blood sugar and supported type 2 diabetes remission at around 6 months versus control.
- Caveat
- Benefits attenuated by 12 months; substantial heterogeneity between trials.
DOI 10.1136/bmj.m4743 · PMID 33441384
Low-carbohydrate diets and metabolic syndrome
Zheng et al. · International Journal of Obesity · 2025
- Design
- Systematic review & meta-analysis (41 RCTs, ~3,806 adults)
- Who
- Adults with metabolic syndrome
- Found
- Low-carbohydrate diets (≥12 weeks) improved BMI, waist circumference, blood pressure, HbA1c, triglycerides, and HDL-cholesterol versus controls.
- Caveat
- Heterogeneity across trials; medium-term follow-up.
DOI 10.1038/s41366-025-01822-5 · PMID 40579564
Two-year nutritional ketosis for type 2 diabetes (Virta)
Athinarayanan et al. · Frontiers in Endocrinology · 2019
- Design
- 2-year non-randomized clinical trial (continuous remote care)
- Who
- Adults with type 2 diabetes
- Found
- A continuous-care intervention with nutritional ketosis sustained glycemic improvement and reduced diabetes medication use over two years.
- Caveat
- Non-randomized, selected participants; the remote-care model is a confound.
DOI 10.3389/fendo.2019.00348 · PMID 31231311
Fasting
Alternate-day fasting combined with a low-carbohydrate diet
Kalam et al. · Obesity Science & Practice · 2019
- Design
- Single-arm pilot study
- Who
- Adults with obesity
- Found
- Pairing alternate-day fasting with low-carb eating produced weight loss and metabolic improvements over the study period.
- Caveat
- Small, single-arm pilot with no control group.
DOI 10.1002/osp4.367 · PMID 31890243
Intermittent fasting and health outcomes (umbrella review)
Sun et al. · eClinicalMedicine · 2024
- Design
- Umbrella review of systematic reviews/meta-analyses of RCTs
- Who
- Adults
- Found
- Intermittent fasting showed benefits for weight and some metabolic markers, but frequently performed similarly to simple calorie restriction.
- Caveat
- Quality varied across the included reviews.
DOI 10.1016/j.eclinm.2024.102519 · PMID 38500840
Medication
STEP 1: once-weekly semaglutide for weight management
Wilding et al. · New England Journal of Medicine · 2021
- Design
- 68-week randomized controlled trial
- Who
- Adults with overweight or obesity (without diabetes)
- Found
- Once-weekly semaglutide 2.4 mg produced about 14.9% mean weight loss over 68 weeks versus 2.4% with placebo.
- Caveat
- On-treatment effect of a medication; not a diet study.
DOI 10.1056/NEJMoa2032183 · PMID 33567185
Weight regain after withdrawal of semaglutide (STEP 1 extension)
Wilding et al. · Diabetes, Obesity and Metabolism · 2022
- Design
- Off-treatment extension of the STEP 1 trial
- Who
- A subset of STEP 1 participants
- Found
- One year after stopping semaglutide (and lifestyle support), participants regained about two-thirds of their prior weight loss.
- Caveat
- Observational extension in a participant subset.
DOI 10.1111/dom.14725 · PMID 35441470
Berberine and obesity indices (dose-response meta-analysis)
Xiong et al. · Complementary Therapies in Clinical Practice · 2020
- Design
- Dose-response meta-analysis of RCTs
- Who
- Adults
- Found
- Berberine did not significantly change body weight (−0.11 kg, not significant), but produced small significant reductions in BMI (about 0.29 kg/m²) and waist circumference (about 2.75 cm) — modest, and far smaller than GLP-1 drug effects.
- Caveat
- Supplement-trial heterogeneity; the body-weight effect was not significant and the others are small.
DOI 10.1016/j.ctcp.2020.101113 · PMID 32379652
Biomarker
Clinical targets for continuous glucose monitoring (time in range)
Battelino et al. · Diabetes Care · 2019
- Design
- International consensus recommendations
- Who
- People using CGM
- Found
- Defined standardized continuous-glucose-monitoring targets, including "time in range" (70–180 mg/dL), for interpreting CGM data.
- Caveat
- Consensus guidance, not an outcomes trial.
DOI 10.2337/dci19-0028 · PMID 31177185
Homeostasis model assessment (HOMA-IR)
Matthews et al. · Diabetologia · 1985
- Design
- Methodology paper
- Who
- Adults
- Found
- Introduced HOMA-IR, a way to estimate insulin resistance from fasting glucose and insulin — still widely used as a research proxy.
- Caveat
- A model/estimate, less standardized clinically than glucose or HbA1c.
DOI 10.1007/BF00280883 · PMID 3899825
Safety
Low-carb/keto diets and lipids (National Lipid Association statement)
Kirkpatrick et al. · Journal of Clinical Lipidology · 2019
- Design
- Scientific statement / evidence review
- Who
- General adult population
- Found
- Low-carb and ketogenic diets can lower triglycerides and raise HDL, but LDL-cholesterol rises in some people — so lipids should be monitored.
- Caveat
- Narrative scientific statement, not a single trial.
DOI 10.1016/j.jacl.2019.08.003 · PMID 31611148
Kidney stones on the ketogenic diet (systematic review)
Acharya et al. · Diseases · 2021
- Design
- Systematic review & meta-analysis
- Who
- People on ketogenic diets (mostly therapeutic)
- Found
- Pooled kidney-stone incidence on ketogenic diets was about 5.9% (around 7.9% in adults) over ~3.7 years of follow-up.
- Caveat
- Mostly therapeutic ketogenic diets, more restrictive than carb fasting.
DOI 10.3390/diseases9020039 · PMID 34070285
Adapting diabetes medication for low-carb eating
Murdoch et al. · British Journal of General Practice · 2019
- Design
- Practical clinical guide
- Who
- Adults with type 2 diabetes on medication
- Found
- Provides a practical protocol for lowering diabetes medications (especially insulin and sulfonylureas) when starting low-carb, to avoid hypoglycemia.
- Caveat
- Practical guidance for clinicians, not a trial.
DOI 10.3399/bjgp19X704525 · PMID 31249097
Putting this into practice? See the protocol,
or read the science in plain language.